I used the new one i bought and used Injuneers info and found that the distance and if the surface is shinny made a hugh difference in temperature. I was able to get reading closer to the ones i wanted to see. I figure the 2 up front would be cooler and they were and i never saw a reading over 300 after 10 minutes so maybe the older gauge is bad since it would go to 800+ way to fast. I changed the plugs and did compression test on 3 of the cylinders. I quit after a couple hours since the compression tester was a screw in and it took over 1 hour on each of them to thread them in and those were the easy ones! . I got 180 on two of them and 150 on the other. I'll never do that again. I put the NGK TR6 and gapped them .030 and it runs way better but now i have a very loud ticking that i can hear from inside. I hopes it a broken spring or loose rocker but maybe its just a loose plug.